html,body{
  padding: 0;
  margin: 0;
  width: 100%;
  height: 100vh;
}
.main{
  width:90%;
  height:80%;
  margin:30px auto
}
.main p{
  margin-bottom:15px;
  margin-top:15px
}
.main input{
  width:120px;
  height:40px;
  font-size:.8em
}
#formula{
  width:250px
}